Plasma CVD apparatus for large area CVD film

ABSTRACT

A plasma CVD apparatus includes first and second electrodes, neutral gas introduction pipes, and a plasma confining electrode interposed between the first and second electrodes to separate a plasma generation region and a substrate processing region. The plasma confining electrode has a hollow structure defined by an upper electrode plate, and a lower electrode plate, and has gas diffusing plates provided in the hollow structure, and has radical passage holes provided to supply radicals from the plasma generation region into the substrate processing region while isolating from a neutral gas. The plasma confining electrode is connected to the neutral gas introduction pipes, and a plurality of neutral gas passage holes are provided for each of the lower electrode plate and the gas diffusing plates to supply the neutral gas into the substrate processing region. A total opening area of the plurality of neutral gas passage holes in the gas diffusing plate on a side of the upper electrode plate is smaller than that of the plurality of neutral gas passage holes in the gas diffusing plate on a side of the lower electrode plate.

This is a divisional of application Ser. No. 09/706,818 filed Nov. 7,2000 now U.S. Pat. No. 6,663,715, the disclosure of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a plasma CVD method of using a plasmaCVD apparatus. More particularly, the present invention relates to aplasma CVD apparatus in which a plasma generation region and a substrateprocessing region are separated and which is suitable for a large areaCVD film formation.

2. Description of the Related Art

As one of the plasma CVD apparatuses for forming a film on a substratewhile restraining plasma damage, a remote-plasma CVD apparatus is knownin which a plasma generation region and a substrate processing regionare separated. A method of forming a CVD film using such a remote-plasmaCVD apparatus is an important technology as the processing process tomake a highly reliable device and a highly efficient device in asemiconductor device process. The remote plasma CVD apparatuses canattain the large sized substrate processes such as a large area flatpanel display switching transistor forming process, a drive circuittransistor forming process and a large diameter silicon wafer process.As such a remote plasma CVD apparatus, a parallel plate remote plasmaCVD apparatus is disclosed in Japanese Laid Open Patent Application(JP-A-Heisei 5-21393). As shown in FIG. 1, the parallel plate remoteplasma CVD apparatus is composed of a high frequency applied electrode101 and a counter electrode 102 on which a substrate 103 is mounted. Aplasma confining electrode 108 as a mesh plate having a plurality ofholes is provided between the high frequency applied electrode 101 andthe counter electrode 102. Plasma 106 is confined between the highfrequency applied electrode 101 and the plasma confining electrode 108.Plasma generation gases 111 are introduced between the high frequencyapplied electrode 101 and the plasma confining electrode 108. The vacuumchamber 107 is provided with an exhaust port 116.

Such a parallel plate remote plasma CVD apparatus using the plasmagenerated between parallel plates can uniformly supply radicalsnecessary to process a substrate in a large area. The apparatusdisclosed in the above mentioned Japanese Laid Open Patent Application(JP-A-Heisei 5-21393) is provided with neutral gas injection holes 109near the passage holes 105 for the radicals 104. The large area uniformprocess is possible through the reaction of the radicals 104 and theneutral gas 110. For this reason, the parallel plate remote plasma CVDapparatus is considered as a superior technique for forming a siliconoxide film and a nitride silicon film as a gate insulating film of athin film transistor on a large sized glass substrate, an amorphoussilicon film such as an active layer and a gate electrode of the thinfilm transistor on the large sized glass substrate, and a silicon oxidefilm and a nitride silicon film as an interlayer insulating film of atransistor device on a large sized silicon substrate.

As mentioned above, the neutral gas injection holes 109 are providednear the radical passage holes 105 and the neutral gas is uniformlysupplied on the surface from the neutral gas injection holes 109. Atthis time, the plasma confining electrode 108 of a hollow structure isused, as disclosed in Japanese Laid Open Patent Application (JP-A-Heisei5-21393). The plasma confining electrode 108 of the hollow structure isprovided with the radical passage holes 105 and the neutral gas passageholes 109 independently, as shown in FIGS. 2 and 3. The radicals 104 andthe neutral gas 110 are never mixed in the hollow structure.

As a method of supplying the neutral gas from the outside of a vacuumchamber 107 to the plasma confining electrode 108 of the hollowstructure, various methods are considered. In a first method, theneutral gas 110 is supplied from an upper direction into the plasmaconfining electrode 108 through the plasma region 106 by neutral gasintroduction pipes 112 as shown in FIG. 4. Also, in a second method, theneutral gas 110 is supplied from a lateral direction into the plasmaconfining electrode 108 as shown in FIG. 5. The method disclosed in theabove-mentioned Japanese Laid Open Patent Application (JP-A-Heisei5-21393) is of the latter.

In the first method shown in FIG. 4, the neutral gas 110 can beuniformly injected on the surface of the substrate, if a lot of neutralgas introduction pipes 112 are uniformly provided for the plasmaconfining electrode 108. In this case, however, the neutral gasintroduction pipes 112 pass through the plasma generation region 106. Asa result, abnormal discharge 117 is generated easily near the neutralgas introduction pipe on the whole of the plasma confining electrode108, so that the plasma generating state becomes unstable.

Also, in the second method shown in FIG. 5, most of the gas is injectedfrom the neutral gas injection holes near the connection section of theneutral gas introduction pipe 112 with the plasma confining electrode108. As a result, because the pressure in the plasma confining electrode108 of the hollow structure is as low pressure as tens to hundreds mtorrwhich is equal to a film forming pressure in the substrate processingregion, the uniform gas injection on the surface is difficult, asschematically shown in FIG. 6.

To solve the above problem, it would be necessary to arrange such a gasdiffusing plate as used in a gas shower head of the conventionalparallel plate plasma CVD apparatus, in the inside of the plasmaconfining electrode 108 of the hollow structure. As shown in FIG. 7, theconventional gas shower head structure is composed of neutral gasintroduction pipes 112, a diffusing plate 114 having a plurality ofholes uniformly provided on the surface thereof and a gas injectionplate 115 having gas injection holes uniformly on the surface thereof.In the conventional parallel plate plasma CVD apparatus, a large numberof gas supply pipes can be connected to the gas shower head. Therefore,uniform gas injection is possible even in the structure as shown in FIG.7. In this case, however, it is impossible to supply a gas to the gasshower head while avoiding the above-mentioned abnormal discharge in theremote plasma CVD apparatus. Also, it is difficult to uniformly injectthe neutral gas on the surface of the substrate 103 in the method ofusing the gas diffusing plate as shown in FIG. 7.

In conjunction with the above description, a plasma CVD apparatus isdisclosed in Japanese Laid Open Utility Model Application (JU-A-Heisei1-86227). In this reference, the plasma CVD apparatus is composed of abox electrode, and a counter electrode. A substrate is provided betweenthe electrodes. The box electrode has a fixed intermediate diffusingplate and a movable intermediate diffusing plate. The diffusing plateshave a plurality of holes. By adjusting the position of the movableintermediate diffusing plate, the number of gas passable holes and thearea of the gas passage hole are adjusted.

Also, a plasma CVD apparatus disclosed in Japanese Laid Open UtilityModel Application (JU-A-Heisei 7-27149). In this reference, the plasmaCVD apparatus is composed of an electrode section (2) having electrodeplates (3 and 4) parallel to a wafer W and a gas introduction pipe (5).A gas G is introduced through the gas introduction pipe (5), passesthrough the electrode plates (3 and 4), and is supplied to the wafer W.A gas diffusing pipe (10 a) is provided in parallel to the electrodeplates (3 and 4) to have holes (11) in a radial direction from the gasintroduction pipe (5). The gas diffusing pipe (10 a) is connected to theconnection end (5 a) of the gas introduction pipe (5) and has the closedend.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide a plasma CVDapparatus in which it is possible to uniformly inject a neutral gas on asubstrate surface.

Another object of the present invention is to provide a plasma CVDapparatus in which abnormal discharge does not occur, even if a neutralgas introduction pipe is inserted into a plasma generation region.

In order to achieve an aspect of the present invention, a plasma CVDapparatus includes first and second electrodes, neutral gas introductionpipes, and a plasma confining electrode interposed between the first andsecond electrodes to separate a plasma generation region and a substrateprocessing region. The plasma confining electrode has a hollow structuredefined by an upper electrode plate, and a lower electrode plate, andhas gas diffusing plates provided in the hollow structure, and hasradical passage holes provided to supply radicals from the plasmageneration region into the substrate processing region while isolatingfrom a neutral gas. The plasma confining electrode is connected to theneutral gas introduction pipes, and a plurality of neutral gas passageholes are provided for each of the lower electrode plate and the gasdiffusing plates to supply the neutral gas into the substrate processingregion. A total opening area of the plurality of neutral gas passageholes in the gas diffusing plate on a side of the upper electrode plateis smaller than that of the plurality of neutral gas passage holes inthe gas diffusing plate on a side of the lower electrode plate.

Here, the number of the neutral gas passage holes in the gas diffusingplate on the side of the lower electrode plate may be more than thenumber of the neutral gas passage holes in the gas diffusing plate onthe side of the upper electrode plate.

Also, first ones of the plurality of neutral gas passage holes in eachof the gas diffusing plates may be different in diameter from secondones of the plurality of neutral gas passage holes in each of the gasdiffusing plates.

Also, positions of the neutral gas passage holes in the gas diffusingplate nearer to the lower electrode plate may be different frompositions of the neutral gas passage holes in the gas diffusing platenearer to the upper electrode plate.

Also, a region of the neutral gas passage holes in the gas diffusingplate nearer to the lower electrode plate may be arranged in an outsideregion of a region of the neutral gas passage holes in the gas diffusingplate nearer to the upper electrode plate.

Also, the gas introduction pipes may extend from a lateral direction ofthe plasma confining electrode to be coupled to side portions of theplasma confining electrode. Instead, the gas introduction pipes mayextend to pass through a peripheral portion of the plasma generationregion to be coupled to upper portions of the plasma confiningelectrode.

In order to achieve another aspect of the present invention, a plasmaCVD apparatus includes first and second electrodes, neutral gasintroduction pipes, and a plasma confining electrode interposed betweenthe first and second electrodes to separate a plasma generation regionand a substrate processing region. The plasma confining electrode has ahollow structure defined by an upper electrode plate, and a lowerelectrode plate, and has gas diffusing plates provided in the hollowstructure, and has radical passage holes provided to supply radicalsfrom the plasma generation region into the substrate processing regionwhile isolating from a neutral gas. The plasma confining electrode isconnected to the neutral gas introduction pipes, and a plurality ofneutral gas passage holes are provided for each of the lower electrodeplate and the gas diffusing plates to supply the neutral gas into thesubstrate processing region. A distribution density of opening areaconsisting of the plurality of neutral gas passage holes is higher in acentral portion of each of the gas diffusing plates than in a peripheralportion thereof.

Here, the number of the neutral gas passage holes in the gas diffusingplate on the side of the lower electrode plate may be more than thenumber of the neutral gas passage holes in the gas diffusing plate onthe side of the upper electrode plate.

Also, first ones of the plurality of neutral gas passage holes in eachof the gas diffusing plates may be different in diameter from secondones of the plurality of neutral gas passage holes in each of the gasdiffusing plates.

Also, positions of the neutral gas passage holes in the gas diffusingplate nearer to the lower electrode plate may be different frompositions of the neutral gas passage holes in the gas diffusing platenearer to the upper electrode plate.

Also, a region of the neutral gas passage holes in the gas diffusingplate nearer to the lower electrode plate may be arranged in an outsideregion of a region of the neutral gas passage holes in the gas diffusingplate nearer to the upper electrode plate.

Also, the gas introduction pipes may extend from a lateral direction ofthe plasma confining electrode to be coupled to side portions of theplasma confining electrode. Instead, the gas introduction pipes mayextend to pass through a peripheral portion of the plasma generationregion to be coupled to upper portions of the plasma confiningelectrode.

In order to achieve still another aspect of the present invention, aplasma CVD apparatus includes first and second electrodes, neutral gasintroduction pipes, a plasma confining electrode interposed between thefirst and second electrodes to separate a plasma generation region, anda gas supply section interposed between the plasma confining electrodeand the second electrode to supply neutral gas. The gas supply sectionhas a hollow structure defined by an upper plate and a lower plate, andhas gas diffusing plates provided in the hollow structure, and hasradical passage holes provided to supply radicals while isolating from aneutral gas. The gas supply section is connected to the neutral gasintroduction pipes, and a plurality of neutral gas passage holes areprovided for each of the lower plate and the gas diffusing plates tosupply the neutral gas into the substrate processing region. A totalopening area of the plurality of neutral gas passage holes in the gasdiffusing plate on a side of the upper plate is smaller than that of theplurality of neutral gas passage holes in the gas diffusing plate on aside of the lower plate.

Here, the number of the neutral gas passage holes in the gas diffusingplate on the side of the lower gas supply section plate may be more thanthe number of the neutral gas passage holes in the gas diffusing plateon the side of the upper gas supply section plate.

Also, first ones of the plurality of neutral gas passage holes in eachof the gas diffusing plates may be different in diameter from secondones of the plurality of neutral gas passage holes in each of the gasdiffusing plates.

Also, positions of the neutral gas passage holes in the gas diffusingplate nearer to the lower gas supply section plate may be different frompositions of the neutral gas passage holes in the gas diffusing platenearer to the upper gas supply section plate.

Also, a region of the neutral gas passage holes in the gas diffusingplate nearer to the lower gas supply section plate may be arranged in anoutside region of a region of the neutral gas passage holes in the gasdiffusing plate nearer to the upper gas supply section plate.

Also, the gas introduction pipes may extend from a lateral direction ofthe gas supply section to be coupled to side portions of the gas supplysection.

Also, the gas introduction pipes may extend to pass through a peripheralportion of the plasma generation region to be coupled to upper portionsof the gas supply section.

In order to achieve yet still another aspect of the present invention, aplasma CVD apparatus includes first and second electrodes, neutral gasintroduction pipes, a plasma confining electrode interposed between thefirst and second electrodes to separate a plasma generation region, anda gas supply section interposed between the plasma confining electrodeand the second electrode to supply neutral gas. The gas supply sectionhas a hollow structure defined by an upper plate and a lower plate, andhas gas diffusing plates provided in the hollow structure, and hasradical passage holes while isolating from a neutral gas. The gas supplysection is connected to the neutral gas introduction pipes, and aplurality of neutral gas passage holes are provided for each of thelower plate and the gas diffusing plates to supply the neutral gas intothe substrate processing region. A distribution density of opening areaconsisting of the plurality of neutral gas passage holes is higher in acentral portion of each of the gas diffusing plates than in a peripheralportion thereof.

Here, the number of the neutral gas passage holes in the gas diffusingplate on the side of the lower electrode plate may be more than thenumber of the neutral gas passage holes in the gas diffusing plate onthe side of the upper electrode plate.

Also, first ones of the plurality of neutral gas passage holes in eachof the gas diffusing plates may be different in diameter from secondones of the plurality of neutral gas passage holes in each of the gasdiffusing plates.

Also, positions of the neutral gas passage holes in the gas diffusingplate nearer to the lower gas supply section plate are different frompositions of the neutral gas passage holes in the gas diffusing platenearer to the upper gas supply section plate.

Also, a region of the neutral gas passage holes in the gas diffusingplate nearer to the lower gas supply section plate is arranged in anoutside region of a region of the neutral gas passage holes in the gasdiffusing plate nearer to the upper gas supply section plate.

Also, the gas introduction pipes may extend from a lateral direction ofthe plasma confining electrode to be coupled to side portions of the gassupply section.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a first conventional plasma CVDapparatus;

FIG. 2 is a cross section showing of a plasma confining electrode havinga hollow structure in detail in the first conventional plasma CVDapparatus shown in FIG. 1;

FIG. 3 is a plan view showing the plasma confining electrode having thehollow structure in the first conventional plasma CVD apparatus;

FIG. 4 is a cross sectional view showing a second conventional plasmaCVD apparatus;

FIG. 5 is a cross sectional view showing a third conventional plasma CVDapparatus;

FIG. 6 is a cross sectional view showing an electrode structure in thethird conventional plasma CVD apparatus in detail;

FIG. 7 is a cross sectional showing another electrode in a fourthconventional plasma CVD apparatus;

FIG. 8 is a cross sectional view showing a plasma CVD apparatusaccording to a first embodiment of the present invention;

FIG. 9 is a cross sectional view showing a part of the plasma CVDapparatus shown FIG. 8 in detail;

FIGS. 10A and 10B are plan views showing an upper plate and lower plateof an electrode, respectively;

FIGS. 11A and 11B are plan views showing first and second diffusingplates, respectively;

FIGS. 12A, 12B, 12C and 12D are graphs showing concentrationdistributions of gas passing through the diffusing plate;

FIGS. 13A, 13B and 13C are plan views showing first, second and thirddiffusing plates, respectively;

FIGS. 14A and 14B are plan views showing the other first and seconddiffusing plates, respectively;

FIG. 15 is a cross sectional view showing the plasma CVD apparatusaccording to a second embodiment of the present invention; and

FIG. 16 is a cross sectional view of the plasma CVD apparatus accordingto a third embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A plasma CVD apparatus of the present invention will be described belowin detail with reference to the attached drawings.

FIG. 8 is a diagram showing the structure of the plasma CVD apparatusaccording to an embodiment of the present invention. The plasma CVDapparatus is used for the formation of a silicon oxide film, forexample. Referring to FIG. 8, the plasma CVD apparatus such as aparallel plate remote plasma CVD is composed of a high frequency appliedelectrode 2 of a plate form, a counter electrode 3 of a plate form and aplasma confining electrode 5 which are provided in a vacuum chamber 1.The counter electrode 3 is located oppositely to the high frequencyapplied electrode 2 and these electrodes are parallel to each other. Asubstrate 4 is mounted on the surface of the counter electrode 3. Theplasma confining electrode 5 is interposed between the high frequencyapplied electrode 2 and the counter electrode 3 to confine plasma. Theplasma confining electrode 5 is grounded. Neutral gas introduction pipes6 are inserted from the vacuum chamber 1 and are connected with theplasma confining electrode 5. The neutral gas introduction pipe 6supplies a neutral gas into the plasma confining electrode 5. Theneutral gas is a non-excited and non-ionized gas. A gas diffusing platesection 7 is arranged in the plasma confining electrode 5.

As shown in FIG. 9, the plasma confining electrode 5 is composed of aplasma confining electrode upper plate 8 and a plasma confiningelectrode lower plate 9. The four side planes or whole side planes ofthe plasma confining electrode 5 are almost closed by side plates (notshown). The gas diffusing plate section 7 is put in a space between theplasma confining electrode upper plate 8 and the plasma confiningelectrode lower plate 9 to uniformly diffuse the neutral gas. The gasdiffusing plate section 7 is formed from a first gas diffusing plate 11and a second gas diffusing plate 12.

The plasma confining electrode 5 has a plurality of radical passageholes 13. The plurality of radical passage holes 13 are formed such thatthe radicals can flow through the plasma confining electrode 5 into alower direction. The plurality of radical passage holes 13 are providedand arranged to have a suitable distribution of the holes 13 such thatthe radicals can diffuse in a uniform surface density. The radicalpassage hole 13 is designed to have a diameter equal to or less thantwice of the Debye length of a generated oxygen plasma such that it ispossible to confine the generated oxygen plasma efficiently.

The first gas diffusing plate 11 has a plurality of first neutral gaspassage holes 14, and second gas diffusing plate 12 has a plurality ofsecond neutral gas passage holes 15. A plurality of third neutral gaspassage holes 16 are formed in the plasma confining electrode lowerplate 9.

FIGS. 10A and 10B show examples of the holes formed on the plasmaconfining electrode upper plate 8 and the plasma confining electrodelower plate 9, respectively. The radical passage holes 13 are uniformlyformed in the plasma confining electrode upper plate 8. The radicalpassage holes 13 and the third neutral gas passage holes 16 areuniformly formed in the plasma confining electrode lower plate 9.

FIG. 11A shows the first gas diffusing plate 11, and FIG. 11B shows thesecond gas diffusing plate 12. The first neutral gas passage holes 14are formed in the neighbor of the center of the first gas diffusingplate 11. The second neutral gas passage holes 15 are formed in thesecond gas diffusing plate 12 on the positions determined based on thoseof the first neutral gas passage holes 14 of the first gas diffusingplate 11. Further, the second neutral gas passage holes 15 are formed ina region extending outside the region where the first neutral gaspassage holes 14 are formed.

As shown in FIG. 9, a mono-silane gas 19 as the neutral gas is suppliedfrom the neutral gas introduction pipe 6 into a space between plasmaconfining electrode upper plate 8 and first gas diffusing plate 11. Themono-silane gas 19 is made uniform by the first neutral gas passageholes 14 of the first gas diffusing plate 11. The passed mono-silane gas19 is further made uniform by the second neutral gas passage holes 15 ofthe second gas diffusing plate 12. The mono-silane gas 19 is injectedtoward the counter electrode 3 (FIG. 8) uniformly on the substratesurface from the third neutral gas passage holes 16 of the plasmaconfining electrode lower plate 9. Only the first gas diffusing plate 11and the second gas diffusing plate 12 are shown in FIG. 9, but thenumber of diffusing plates is not limited to the two, and may be more.Also, the number of pipes 6 is not limited to 2. It would be moredesirable that four or more pipes are used.

A silicon oxide film is formed by such a plasma CVD apparatus. As shownin FIG. 8, an oxygen gas 18 is introduced between the high frequencyapplied electrode 2 and the plasma confining electrodes 5 in the vacuumchamber 1. Then, the glow discharge is generated to generate oxygenplasma 22 in a plasma generation region. The generated oxygen plasma 22is efficiently confined between the high frequency applied electrode 2and the plasma confining electrode 5. As a result, the plasma density inthe oxygen plasma 22 is about 10¹⁰/cm³, while the plasma density betweenthe plasma confining electrode 5 and the counter electrode 3 is 10⁵ to10⁶/cm³. In this case, electrons, oxygen atom ions, oxygen moleculeions, oxygen atom radicals, and oxygen molecule radicals exist in theoxygen plasma. However, the electrons and ions going out of the plasmaare negligible. Therefore, the oxygen atom radicals and oxygen moleculeradicals react with the mono-silane gas 19 and contribute to theformation of the silicon oxide film through the reaction with themono-silane gas 19. Hereinafter, these radicals are merely referred toas oxygen radicals. The oxygen radicals 21 pass through the radicalpassage holes 13 to diffuse in the substrate processing region, andreact with the mono-silane gas 19 which passes through the third neutralgas passage holes 16 to form the silicon oxide precursor such as SiOxand SiOxHy. Thus, the silicon oxide film is formed on the substrate 4.

As described above, the plasma density between the plasma confiningelectrode 5 and the counter electrode 3 becomes very low. Therefore, theplasma damage to the substrate 4 becomes very low in the presentinvention, compared with the conventional parallel plate plasma CVD.This effect appears conspicuously in case of the silicon surface onwhich a MOS structure is formed. When the silicon oxide (SiO₂) film isformed on a single crystal silicon substrate by the conventionalparallel plate plasma CVD, a MOS interface trapped charge density is10¹¹ to 10¹²/cm²/eV near the mid-gap. On the other hand, when thesilicon oxide film is formed by the parallel plate remote plasma CVD ofthe present invention, the interface trapped charge density is as low as10¹⁰ /cm²/eV.

In this way, in the plasma confining electrode 5, it is important howthe first and second gas passage holes 14 and 15 are formed in theplurality of gas diffusing plates 11 and 12 which are disposed in thehollow structure between the plasma confining electrode upper plate 8and the plasma confining electrode lower plate 9. If the holes 14 and 15are suitably arranged, the injection of the mono-silane gas 19 from thethird neutral gas passage holes 16 can be made uniform. Thus, thedistribution of the precursor of the silicon oxide on the substrate canbe made uniform, so that the uniformity of the silicon oxide film onsubstrate 4 is improved.

The flow of the mono-silane gas in the plasma confining electrode 5 inthe above-mentioned embodiment will be described with reference to FIGS.12A to 12D.

(1) The mono-silane gas 19 is supplied between the plasma confiningelectrode upper plate 8 and the first gas diffusing plate 11. As shownin FIG. 12A, the concentration distribution of the mono-silane gas atthis time point is high in the periphery and low in the center.

(2) After the mono-silane gas passes through the neutral gas passageholes 14 nearby of the center of the first gas diffusing plate 11, theconcentration distribution of the mono-silane gas is low in theperiphery and high in the center, as shown in FIG. 12B. The neutral gasintroduction pipes 6 do not pass through the plasma generation region,and the distribution of holes in the diffusing plates is improved. Inthis way, the high gas concentration distribution in the center isrealized.

(3) As shown in FIG. 12C, after the mono-silane gas passes through thesecond neutral gas passage holes 15 of the second gas diffusing plate12, the concentration distribution of the mono-silane gas hasinclination more gentle than the concentration distribution shown inFIG. 12B based on the distribution of the second neutral gas passageholes 15.

(4) As shown in FIG. 12D, after the mono-silane gas passes through thethird neutral gas passage holes 16 of the plasma confining electrodelower plate 9, the concentration distribution of the mono-silane gasbecomes further gentle, compared with the concentration distributionshown in FIG. 12C. Thus, approximately uniform gas injection on thesubstrate surface is carried out.

In the above-mentioned embodiment, the two gas diffusing plates areused. However, as shown in FIGS. 13A, 13B and 13C, a third gas diffusingplate 12′ may be added. As shown in FIG. 13C, third gas passage holes15′ are formed in the third gas diffusing plate 12′ on the positionsdetermined based on those of the second neutral gas passage holes 15 ofthe second gas diffusing plate 12. Further, the third neutral gaspassage holes 15′ are formed in a region extending outside the regionwhere the second neutral gas passage holes 15 are formed. For furtherimprovement of the diffusion performance, it is desired that four ormore diffusing plates are used. The use of more diffusing plates makesthe gas concentration uniform. However, the use of more diffusing platesintroduces the complicated structure of the plasma confining electrode5. Also, the radical passage hole 13 becomes long.

Moreover, in the embodiment shown in FIGS. 14A and 14B, the secondneutral gas passage holes 15 are formed on the second diffusing plate 12in such a manner that the position of the second neutral gas passageholes 15 do not overlap the first neutral gas passage holes 14. When thepositions of the neutral gas passage holes overlap, there is apossibility that the gas passage route with the same length as thedistance between the diffusing plates exist. A part of the neutral gaspasses through the gas passage holes before the gas diffusion into thelateral direction between the gas diffusing plates. In the examplesshown in FIGS. 14A and 14B, if the positions of the neutral gas passageholes do not overlap, the gas diffusion into the lateral direction canbe promoted.

FIG. 15 shows the structure of the plasma CVD apparatus according to asecond embodiment of the present invention. The method of introducingthe neutral gas in the second embodiment is different from the method inthe first embodiment shown in FIG. 8. Referring to FIG. 15, the neutralgas introduction pipes 6 for neutral gas such as the mono-silane gas areinserted into the vacuum chamber 1 from the side plane of the plasmageneration region, and connected with the upper portions of the plasmaconfining electrode 5. Thus, the neutral gas introduction pipes 6 passesthrough the plasma generation region. However, the passage region is theperipheral portion of the plasma generation region 22. Therefore, thechange of the plasma state is little, even if the abnormal dischargehappens, compared with the case where the abnormal discharge happensnear the upper surface of the plasma confining electrode.

In this way, if the gas diffusing plates are arranged in the plasmaconfining electrode 5, the shape and number of gas diffusing plates canbe changed according to the necessity without leaving from the scope ofthe present invention. Also, the shape and number of neutral gas supplypipes in the second embodiment may be changed according to the necessitywithout leaving from the scope of the present, if the neutral gas issupplied from the outside of the vacuum chamber 1 into the periphery ofplasma confining electrode 5 through the peripheral portion of theplasma generation region.

FIG. 16 shows the structure of the plasma CVD apparatus according to athird embodiment of the present invention. The parallel plate remoteplasma CVD shown in FIG. 16 is different from that of FIG. 8 in thefollowing points. That is, in the third embodiment, the gas supply plate29 is used in place of the plasma confining plate 5. The gas supplyplate 29 is connected to the neutral gas introduction pipes 6 to supplythe neutral gas. Also, the gas supply plate 29 includes theabove-mentioned gas diffusing plate section 7. Thus, the gasconcentration is made uniform by the gas supply plate 29. The gas supplyplate 29 has the same structure of the plasma confined plate 5 shown inFIG. 8 or FIG. 15. Therefore, the examples shown in FIG. 10, FIG. 11,FIG. 13, and FIG. 14 can be applied just as it is, for the diffusingplate section 7 of FIG. 16. If it is possible for the radicals to beuniformly injected, the diameter of each of the radical passage holes13′ of the gas supply plate 29 are optional. Also, it is possible toelectrically use the gas supply plate 29 in the electric floatingcondition without grounding.

In the third embodiment, a plasma confining electrode 5′ is providedbetween the high frequency applied electrode and the gas supply plate 29to confine the generated plasma. The plasma confining electrode 5′ has aplurality of radicals passage holes. Also, the plasma confiningelectrode 5′ is grounded. In the first embodiment of FIG. 8, the plasmaconfining electrode 5 has the gas diffusing function corresponding tothe gas supply plate 29 and the plasma confining function. However, inthe third embodiment of FIG. 16, the plasma confining electrode 5′ hasonly the function to confine the plasma. Thus, the gas diffusingfunction and the plasma confining function are fully separated. Also,the third embodiment can be applied to the second embodiments.

In the above embodiments, the example in which the silicon oxide film isformed using the mono-silane and the oxygen gas is described. However,liquid Si materials such as the high order silanes such as disilane andTEOS (Tetraethoxysilane) in place of mono-silane may be used. Also,nitrogen oxide may be used in place of oxygen. Further, the sameadvantage can be attained with respect to the formation of the plasmaCVD films using the other materials such as a silicon nitride film usingthe mono-silane and ammonia, an amorphous silicon film using themono-silane and hydrogen or inert gas, in place of the formation of thesilicon oxide film.

Moreover, the parallel plate remote plasma CVD apparatus is described.The plasma CVD apparatus has the plasma confining electrode for theplasma separation provided between the plasma generation region and thesubstrate processing region and having the plurality of holes. Thepresent invention can be applied to any types of plasma CVD apparatussuch as a plasma CVD apparatus which uses microwave plasma, electroncyclotron resonance plasma, inductive coupling plasma, and helicon waveplasma.

As described above, a total opening area of the plurality of neutral gaspassage holes in the gas diffusing plate on a side of the upperelectrode plate may be smaller than that of the plurality of neutral gaspassage holes in the gas diffusing plate on a side of the lowerelectrode plate. Also, the number of the neutral gas passage holes inthe gas diffusing plate on the side of the lower electrode plate may bemore than the number of the neutral gas passage holes in the gasdiffusing plate on the side of the upper electrode plate. In addition,first ones of the plurality of neutral gas passage holes in each of thegas diffusing plates may be different in diameter from second ones ofthe plurality of neutral gas passage holes in each of the gas diffusingplates.

Also, positions of the neutral gas passage holes in the gas diffusingplate nearer to the lower electrode plate may be different frompositions of the neutral gas passage holes in the gas diffusing platenearer to the upper electrode plate. In this case, a region of theneutral gas passage holes in the gas diffusing plate nearer to the lowerelectrode plate may be arranged in an outside region of a region of theneutral gas passage holes in the gas diffusing plate nearer to the upperelectrode plate.

Also, a distribution density of the plurality of neutral gas passageholes is higher in a central portion of each of the gas diffusing platesthan in a peripheral portion thereof.

In the plasma CVD apparatus of the present invention, the concentrationof the neutral gas which is injected into the substrate processingregion can be made uniform in the surface.

In the present invention, it is not necessary to pass the gasintroduction pipe through the plasma generation region, specifically,near the center of the plasma generation region. Therefore, the abnormaldischarge never occurs to make the plasma state unstable. The uniformpassage of the neutral gas on the substrate surface becomes possible inthis way. Therefore, the high quality film which does not have a defectdue to the plasma damage can be uniformly formed on the large areasubstrate in the case that a MOS device gate insulating film and aninterlayer insulating film are formed, and a thin-film transistor devicesilicon film and a nitride silicon film are formed.

What is claimed is:
 1. A plasma CVD apparatus comprising: first andsecond electrodes; neutral gas introduction pipes; a plasma confiningelectrode interposed between said first and second electrodes toseparate a plasma generation region; and a gas supply section interposedbetween said plasma confining electrode and said second electrode tosupply said neutral gas, wherein said gas supply section has a hollowstructure defined by an upper plate and a lower plate, and has gasdiffusing plates provided in the hollow structure, and has radicalpassage holes, said gas supply section is connected to said neutral gasintroduction pipes, and a plurality of neutral gas passage holes areprovided for each of said lower plate and said gas diffusing plates tosupply said neutral gas into said substrate processing region, and atotal opening area of said plurality of neutral gas passage holes insaid gas diffusing plate on a side of said upper plate of said gassupply section is smaller than that of said plurality of neutral gaspassage holes in said gas diffusing plate on a side of said lower plateof said gas supply section.
 2. The plasma CVD apparatus according toclaim 1, wherein the number of said neutral gas passage holes in saidgas diffusing plate on the side of said lower said gas supply sectionplate is more than the number of said neutral gas passage holes in saidgas diffusing plate on the side of said upper said gas supply sectionplate.
 3. The plasma CVD apparatus according to claim 1, wherein firstones of said plurality of neutral gas passage holes in each of said gasdiffusing plates are different in diameter from second ones of saidplurality of neutral gas passage holes in each of said gas diffusingplates.
 4. The plasma CVD apparatus according to claim 1, whereinpositions of said neutral gas passage holes in said gas diffusing platenearer to said lower said gas supply section plate are different frompositions of said neutral gas passage holes in said gas diffusing platenearer to said upper said gas supply section plate.
 5. The plasma CVDapparatus according to claim 4, wherein a region of said neutral gaspassage holes in said gas diffusing plate nearer to said lower said gassupply section plate is arranged in an outside region of a region ofsaid neutral gas passage holes in said gas diffusing plate nearer tosaid upper said gas supply section plate.
 6. The plasma CVD apparatusaccording to claim 1, wherein said gas introduction pipes extend from alateral direction of said gas supply section to be coupled to sideportions of said gas supply section.
 7. A plasma CVD apparatuscomprising: first and second electrodes; neutral gas introduction pipes;a plasma confining electrode interposed between said first and secondelectrodes to separate a plasma generation region; and a gas supplysection interposed between said plasma confining electrode and saidsecond electrode to supply said neutral gas, wherein said gas supplysection has a hollow structure defined by an upper plate and a lowerplate, and has gas diffusing plates provided in the hollow structure,and has radical passage holes, said gas supply section is connected tosaid neutral gas introduction pipes, and a plurality of neutral gaspassage holes are provided for each of said lower plate and said gasdiffusing plates to supply said neutral gas into said substrateprocessing region, and a distribution density of opening area consistingof said plurality of neutral gas passage holes is higher in a centralportion of each of said gas diffusing plates than in a peripheralportion thereof.
 8. The plasma CVD apparatus according to claim 7,wherein the number of said neutral gas passage holes in said gasdiffusing plate on the side of said lower gas supply section plate ismore than the number of said neutral gas passage holes in said gasdiffusing plate on the side of said upper gas supply section plate. 9.The plasma CVD apparatus according to claim 7, wherein first ones ofsaid plurality of neutral gas passage holes in each of said gasdiffusing plates are different in diameter from second ones of saidplurality of neutral gas passage holes in each of said gas diffusingplates.
 10. The plasma CVD apparatus according to claim 9, whereinpositions of said neutral gas passage holes in said gas diffusing platenearer to said lower gas supply section plate are different frompositions of said neutral gas passage holes in said gas diffusing platenearer to said upper gas supply section plate.
 11. The plasma CVDapparatus according to claim 10, wherein a region of said neutral gaspassage holes in said gas diffusing plate nearer to said lower gassupply section plate is arranged in an outside region of a region ofsaid neutral gas passage holes in said gas diffusing plate nearer tosaid upper gas supply section plate.
 12. The plasma CVD apparatusaccording to claim 11, wherein said gas introduction pipes extend from alateral direction of said gas supply section to be coupled to side.